Apparatus for transmitting sonic vibrations into liquid bodies



y 1962 A. G. BODINE, JR 3,033,158

APPARATUS FOR TRANSMITTING SONIC VIBRATIONS INTO LIQUID BODIES FiledFeb. 1'7, 1960 5 Sheets-Sheet l JNVENTOR. ALBERT 63 Bow/v.5, we

y 8, 1962 A. G BODINE, JR 3,033,158

APPARATUS FOR TRANSMITTING SONIC VIBRATIONS INTO LIQUID BODIES FiledFeb. 17, 1960 5 Sheets-Sheet 2 INVENTOR.

ALBERT a. um/v.5, (74

y 1962 A. G. BODINE, JR 3,033,158

APPARATUS FOR TRANSMITTING some VIBRATIONS INTO LIQUID BODIES Filed Feb.17, 1960 3 Sheets-Sheet 3 INVEN TOR.

ALBERT 6. BOD/NE, JR

3,033,153 APPARATUS FOR 'ERANSMITTENG SONIC VIBRA- TIONS INTO LIQUIDBODEES Albert G. Bodine, Ira, 13120 Moorpark St, Sherman Oaks, Calif.Filed Feb. 17, 1960, Ser. No. 9,349 7 Claims. (Cl. 116137) Thisinvention relates generally to high power acoustic apparatus forgenerating high energy sound waves of relatively low frequency inliquids, for such purposes as sonic liquid treatment in large processtanks, sonically cleaning large liquid tanks, etc. The invention isuseful also for transmitting high energy pressure waves for substantialdistances through extended bodies of water, such as the ocean, to createan underwater sound field useful in submarine detection.

This application is a continuation-in-part of my copen ing applicationSerial No. 825,117, filed July 6, 1959, entitled Method and Apparatusfor Generating and Transmitting Sonic Vibrations, now Patent No.2,960,314, which was a continuation-in-part of my application Serial No.484,627, filed January 28, 1955, now abandoned.

The invention contemplates very high sonic power, relatively lowfrequency, which, Without intention of limitation, may be typicallybetween 200 and 2000 cycles per second, and rugged mechanicaloscillators for generating the sound waves.

Objects of the invention include the provision of improved sonicprocessing or wave generating apparatus characterized by extraordinarypower, relatively low frequency, simple and rugged mechanicaloscillators of low cost but high reliability, unusually high efiiciencyfor a sonic processing machine, excellent frequency stability, and readyportability.

In accordance with the invention, there is provided a vibratory soundwave radiator in coupling contact with the liquid, preferably in thegeneral form of a flat cone; and to assure good loading of the radiatorby the liquid, the dimension across the surface of the radiator is madeat least a major fraction of a wave length of the sound wave to beradiated thereby, measured in the liquid. An optimum dimension issubstantially one wave length, and a dimension up to two wave lengths,or even more, might in some cases be used, though at such dimension theradiator may be overly large for practical purposes, for reasons thatwill appear.

Assuming a radiator of optimum dimensions, therefore, i.e., one wavelength across, and assuming a frequency of 400 cycles per second, whichis a desirable frequency for many applications, the diameter of theradiator, using a value of 4800 feet per second for the velocity ofsound in water, is of the order of 12 feet. A vibratory radiator of suchscale, immersed in liquid, is heavily loaded, and has a high loadedmechanical impedance. By definition, the mechanical impedance of theliquid-loaded radiator is the complex quotient of the driving force onthe radiator divided by the linear velocity. This factor for such aradiator, as described, is quite high.

One problem presented is to drive this high impedance radiatoreffectively. Simple mechanical oscillators or force generators of highpower types do not characteristically operate at the necessary highoutput impedance for reasonable match to the impedance of the radiator.One type of oscillator that is eminently suitable, excepting for thisproblem, particularly for the high power and frequency range incontemplation, is disclosed in several forms in my aforementioned U.S.Patent No. 2,960,314. This oscillator is of a mechanical type, involvinga cyclically driven relatively small inertia mass body which isoscillative at relatively high velocity in a predetermined path relativeto a body of substantially larger mass which 7 3,033,158 Patented May 8,1962 supports it through suitable constraining means, such as a bearing.The small oscillative mass reacts through such bearing means to exert anreactive oscillating force on the supporting body, causing it to vibratethrough a small amplitude. Because of the relatively large mass of thesupporting body as compared with the mass of the small oscillati'vcbody, there is a large velocity reduction, and correlative force gain,between the small oscillative body and the supporting body. Inconsequence, the force generator so constituted has a fairly ampleoutput impedance; however, it is still so poorly adjusted to the loadedimpedance of the radiator that effective direct drive of the latter bythe generator would not be feasible.

In addition, and as a further major consideration, a force generator ofthe class described can, in accordance with principles disclosed in myaforementioned U.S. Patent No. 2,960,314, be very advantageouslycontrolled to operate at the selected resonant frequency, with goodfrequency stability, high Q, and an important energy storage property(fly-wheel eifect), by coupling it directly to an elastically vibratoryhalf-wavelength bar structure, which vibrates at the desired operatingfrequency in a resonant standing wave pattern, and which is in turncoupled to the device to be driven, in this case, the sound waveradiator. The coupling between the generator and this half-wave standingwave bar structure is made to a velocity antinode at one end of thelatter, where impedance is not too large, and is, in fact, fairly welladjusted to the output impedance of the generator.

Under such conditions the oscillator assembly moves with large vibratoryvelocity, and thus has high power output. The velocity antinode at theopposite end of the bar structure may then be coupled to the device tobe driven. By coupling to a velocity antinode of the bar structure,where impedance is not too high, and is of the order of that of thegenerator, an important advantage is gained, in that the bar structure,vibrating at substantial amplitude at the antinode coupling point,exerts a back reaction through the supporting body of the generator andits bearing means, or other constraining means for the small oscillativeinertia body of the generator, which, further supposing a properlygoverned drive effort on the oscillative body, constrains that body tooscillate at closely controlled frequency which is just underthefrequency for peak resonance. It is critically important that thedriving force on the oscillative body be less than that which would takethe oscillative mass to or over the basic resonant frequency of thesystem. Under such conditions, operating frequency is stabilized, and afairly high frequency operation made possible for a powerful form ofmechanical oscillator.

There still remains, however, the problem of impedance adjustmentbetween that of the force generatorand the high impedance of the largeliquid loaded radiator. The half-wavelength resonant standing wave bar,disclosed in my U.S. Patent No. 2,960,314 and referred to hereinabove,permits effective operation of the generator, but does not, withoutfurther improvement, furnish a sufiiciently high impedance at its outputend for effective drive of this large radiator.

A prerequisite to a good understanding of the present invention, in theaspect of meeting the problem stated in the preceding paragraph, is afull understanding of a halfwavelength standing wave bar, and itsimpedance characteristics, and this subject will next be givenattention.

Assume an elongated steel (elastic) bar, of uniform cross section,suspended in a free-free state, i.e., supported at its mid-point, andfree for longitudinal vibration at both ends. Assume further analternating force generator coupled to one end of the bar, so as toapply a sinusoidal alternating force thereto in a directionlongitudinally of the bar, and at a frequency f equal to S7 2L,

where s is the speed of sound in the material of the bar, and L is thelength of the bar. Under these conditions, alternating sinusoidal wavesof compression and tension are launched by the force generator into thebar. These travel the length of the bar, are reflected from the far endthereof as waves of unlike kind (Le, a wave of compression is reflectedas a wave of tension, and vice versa), and by virtue of interferencebetween the original and reflected waves when f=s/2L, a half-wavelengthresonant standing wave is established. Under these conditions,longitudinal wave amplitude is cancelled at the mid-point of the bar,and is magnified at the two ends thereof. In effect, the two halfportions of the bar alternately elastically elongate and contract, instep with one another, the magnitude of elastic elongation andcontraction increasing progressively from zero, or substantially so, atthe midpoint to maximum at the ends. The condition at the midpoint ofthe bar is called a velocity node, and is characterized by minimizedcyclic velocity amplitude, and by maximized cyclic stress amplitude. Thecondition at each end of the bar is called a velocity antinode, and ischaracterized by maximized cyclic velocity amplitude, and minimizedcyclic stress amplitude.

It will be seen that the mechanical impedance of the velocity antinodesof the halfwave bar is relatively low, and at the velocity node thereofis extremely high. There is a gradual transition of mechanical impedancefrom high at the velocity node to low at the velocity antinodes. At thevelocity antinodes, the impedance is well adjusted to the outputimpedance of a mechanical cyclic force generator of the type hereinabove mentioned, but is far too low for effective drive of the liquidloaded sound radiator.

The present invention meets this last problem by reducing thequarter-wavelength portion of the bar between the velocity node and thecoupling to the radiator to 10% of its original quarter-wavelength, orin other words to the approximate range of typically to wavelength. Theextremity of the shortened one-fifth to one-tenth wavelength portion ofthe bar is then directly coupled to the sound wave radiator. The bar inthis form, so coupled to the radiator, still operates with a standingwave pattern, at the original resonant frequency, but the pattern fromthe node out to the coupling point to the radiator is a small fractionof a quarter-wavelength. And at the ex tremity, which is close spaced tothe node, the mechanical impedance is very high, and of the order ofthat of the liquid loaded radiator.

Thus I have accomplished the diflicult problem of driving a highimpedance liquid loaded sound radiator of large effective area from asimple mechanical oscillator of the type mentioned, with good impedanceadjustment between the generator and the radiator, and with preservationof the desirable back reaction effect which stabilizes the forcegenerator and holds it closely at the predetermined operating frequency,typically just slightly under the peak resonance frequency for thesystem as a whole.

With reference now to the drawings:

FIG. 1 is a view of an illustrative apparatus in accordance with theinvention, partly in side elevation, and partly in longitudinal medialsection;

FIG. 2 is an enlarged section on line 2-2 of FIG. 1;

FIG. 3 is a section on line 33 of FIG. 2;

FIG. 4 is a side elevational view of a modification of the apparatus ofFIG. 1, the radiator being shown in section on a diameter thereof;

FIG. 5 is an enlarged longitudinal section on line 5-5 of FIG. 4;

FIG. 6 is a side elevation of another modification, parts being shown inlongitudinal medial sect-ion;

FIG. 7 shows an apparatus in accordance with the invention incombination with a liquid body in a tank;

FIG. 8 shows an apparatus in accordance with the invention supported inthe ocean from a ship; and

FIG. 9 shows an apparatus in accordance with the invention supported inthe ocean by a buoy.

In FIGS. 1, 2 and 3, an elastic bar 10, preferably steel and in the formof an elongated cyclinder, mounts at one end a sound wave radiator 11,in this case in the form of two flat sheet metal cones, 12, back toback. Secured to the opposite end of a bar 10 is an alternating forcegenerator 13. The force generator 13 is of a type containing a smalloscillative inertia body constrained to move in a predetermined cyclicpath, a number of suitable examples of which are disclosed in myaforementioned application Serial No. 825,l 17. However, I here show atype having eccentrically weighted rotors driven through appropriategearing from an electric motor 14, preferably an induction motor.

Force generator 13 comprises a cylindric body or case 16 having at oneend a threaded coupling pin 17 screwed into a threaded socket at theadjacent end of bar 10, so as to afford a secure, rigid coupling betweenthe generator case and bar 10. Inside case 16 is a series ofeccentrically weighted rotors 18 rotatably mounted through suitablebearings 19 on shafts 20 set into case 16. Spur gears 21 on theperipheries of the rotors mesh with one another, and by inspection, itwill be seen that the rotors are arranged so that their eccentricweights 22 all move longitudinally of bar 10 in synchronism, so thatunbalanced longitudinal components of force are additive, but withalternate rotors turning in opposite directions, so as to canceltransverse force components.

The spur gear 21 on the upper rotor is driven by spur gear 24 on thecross shaft 25 journalled at its ends in case 16, and driven in turnthrough bevel gear 26 meshing with bevel gear 27 on an axial shaft 23journalled in the top end of the case. Shaft 28 has a splined endportion 28a, engaged by a splined socket 29 in the end of shaft 30 ofthe aforementioned drive motor 14.

The case 32 of motor 14 is fastened to one end of a sleeve 33surrounding the force generator, and coupled at its opposite end to oneend of a tubular jacket 34 that surrounds bar 10 and extends towardradiator 11. The opposite end of jacket 34 is connected to one end ofcoupling sleeve 35, the other end of which has an internally tapered endportion 36 joined by a firm taper fit to a complementary tapered surface37 on bar 10, the bar being of somewhat enlarged diameter beyond thistaper, as at 38, within the confines of cones 12, as shown.

Screwed into a socket in the end of bar portion 38 is a plug 39supporting an end cap 40, which furnishes a stud mounting for theinwardly turned end portion 41 of a cone mounting sleeve 42 annularlyspaced around bar portion 38 and supported therefrom by ribs 43. Thecones 12 are furnished withinner flanges 44 which are welded to sleeve42. At their peripheries, the cones 12 contact one another, and aresuitably connected together, as by welding. The outer rims of thesecones 12 are preferably furnished with turned stiffening flanges 46.

As described in the introductory paragraphs hereto, the sound radiatorconstituted by cones 12 has an effective diameter preferably of theorder of a wavelength of sound in the liquid medium in which theapparatus is to operate. For water, this diameter dimension isaccordingly, for a frequency of 400 cycles per second, about 12 feet.The bar 10, calculated on the basis of the speed of sound in steel, fora frequency of 400 cycles per second, has a length of about 10 feet.

The apparatus is immersed in a body of liquid, in any one of a number ofsituations, some of which will be particularized hereinafter, so thatradiator 11 is liquid loaded, and when caused to vibrate effectively incontact with the liquid, radiates a sound wave therefrom.

The electric drive motor drives the shaft of the force generator,causing rotation of the unbalanced rotors; and the longitudinalcomponents of the cyclic reactive forces of these rotors are transmittedthrough the rotor shafts to the generator case, where they are additiveto generate a longitudinal cyclic force on the generator case, which isin turn applied to the end of bar 10. The case of the force generator,and the end portion of bar 10, being at a velocity antinode V of thebar, vibrate longitudinally of the axis of the bar, and the impedance atthe coupling point between generator case and bar is elevatedsubstantially over that of the combination of unbalanced rotors, butmaterially less than that of the liquid loaded radiator 11. The velocitynode of the bar locates itself at V close to the radiator 11, and thedistance between V and V is a quartenwavelength. At the sound radiatorextremity of the bar is a fairly high impedance point, where thevelocity cycle is of relatively small amplitude, and the stress cycle isof relatively high amplitude. The radiator 11 is connected to the bar atthis high impedance point and is driven with a corresponding impedancecharacteristic. This high impedance is well adjusted to the loadedimpedance of the radiator 11, and the latter is therefore effectivelydriven from the force generator, so as to radiate sound waves at highpower.

An advantage of the apparatus of FIGS. 1 and 2 is particularly to benoted, in that whereas the force generator must undergo vibration withthe bar 10, the splined connection between the motor shaft and the forcegenerator shaft permits the motor to remain stationary in space,supported by the jacket 34, which is also stationary by virtue of beingconnected to the bar 10 at a node of the latter.

The drive motor for the force generator has been described as preferablyan induction motor. By using an induction motor with substantialarmature slip in its rotating field, the driving force exerted therebyon the force generator is readily held at a magnitude less than thethreshold value where the frequency generated by the force generatorbreaks over the peak of resonance, as more fully explained in myapplication Serial No. 825,117. This is a feature of marked advantage,giving the system very good frequency stability. Alternative expedientswithin the scope of the invention are available to assure this frequencystability. For example, there can be a torqueresponsive engine-generatorcombination for supplying electric power to the driving motor for theforce generator, which driving motor need not be in such instance aninduction motor. Under such conditions, the torque responsiveness of theengine substitutes for the torque responsiveness of the induction motor,so that the motor generator can be closely coupled, or non-slip, innature. An important feature of my force generator-resonator combinationis that such frequency stability greatly adds to the controllability ofa remotely controlled servo-governor.

It might here be mentioned that it is advantageous in all casese tofabricate the radiator structure of stiff plate or cone members formingan assembly having its first resonant frequency above the resonantfrequency of the resonant bar structure. This keeps the radiatorstructure from flapping owing to resonant frequencies equal to or belowthe operating frequency of the system.

FIGS. 4 and 5 show a modified resonant bar structure, and modifiedmounting of the periodic force generator and drive motor. A cone typesound radiator of the type of that of FIG. 1 is shown at 50. A forcegenerator is shown at 51, and an electric drive motor at 52, themodified resonant far structure being designated generally at C.

The force generator is of the type of that shown in FIGS. 13, havingcase 53 bolted at 54 to the bar structure, unbalanced rotors 55 gearedtogether by gears 56 and driven through gears 57, 58 and 59 from motorshaft 60, the motor case 61 being in this instance screwed into the endof the generator case, as shown.

The bar structure C in this instance comprises a plurality of elasticcylindrical rods or tubes 64, integrally joined into a single head 66which is bolted at 54 to the force generator case.

The rods 64 diverge from head 66 at a typical angle as shown, and theirextremities are furnished with mounting plates 69 bolted to the rearwardside of the radiator assembly in the region of the line of inertiathereof. These may be two diametrically opposite rods 64, or four, ashere shown, or a greater number. In fact, there may be sufiicient ofsuch rods to form a full cone, or an integral cone may be used. Ofcourse, the more rods, the less will be their individual cross sectionareas.

The apparatus of FIGS. 4 and S operates with a velocity antinode at V, avelocity node in each rod 64 at V relatively close spaced to theradiator, and a region of high impedance at the junctions of each rodwith the radiator. The standing Wave patterns in the rods 64 are alike,and of course similar to those in the bar 10 of the embodiment of FIGS.1-3. The advantage of the bar structure of FIGS. 4 and 5 is the locationof the point of radiator drive well out on the cone assembly where thedrive effort results in minimum bending of the latter.

In FIG. 6 is shown a modified form of the invention in which theresonant bar structure 7% is flared out at one end to constitute thesound radiator. To the small end of the bar structure 70 is bolted thecase of the periodic force generator 71, whose drive shaft is drivenfrom the drive shaft of electric motor 72, in an arrangement generallylike that of FIGS. l-3. The bar structure 70 is flared from its smallend in the general form of an 'ex ponential horn. It may be a casting ofa material such as anodized aluminum, and may be cast with cavities 73for lightness. A horn-like shell 74, configured to the general outlineof the bar structure 70, surrounds the sides of the bar structure withclearance, and encloses force generator 71, being bolted to the case ofmotor 72, and to the bar structure in the plane of the velocity node Vof the latter, as by means of spacing webs 77 and screws 73. The shell74 is here shown as formed with eyes 79 to which supporting cables $0may be conveniently connected. In resonant operation, a velocityantinode V appears at the small end of the bar structure, a region ofhigh impedance appears at the front radiating face 81 of the barstructure. The mechanical impedance characteristics are similar to thoseof the previously described embodiments.

Operation is in general the same as that of the embodiments of FIGS.l-S, with the exception that the exponential shape tends to make theacoustic structure more unidirectional as regards the sound waveradiation pattern.

To improve the unidirectional Wave radiation quality, provisions may bemade for decoupling the back side of the horn-shaped bar structure, sothat substantially only the front face 81 is acoustically coupled to theliquid, and thus so that radiation is primarily out from, and along theaxis of, the main radiating surface 81. To this end, I coat the backsurface of the flared portion of the bar structure with a layer 82 ofcellular elastomer such as cellular rubber. This material tends tocompress and expand in step with vibration of the bar structure, andeffectively prevents back sound wave radiation. Various decouplingprovisions for a similar purpose were disclosed in my Patent No.2,717,763.

At greater depths, the cellular material tends to become collapsed, anda more positive decoupling means is required if a monopole radiationpattern is to be achieved. In such case, an annular flexible diaphragm84 is fastened to the periphery of the front face 81 of the flared barstructure and to the periphery of the horn shaped shell 74, so as toform a closed gas space 85 between the back of the flared bar structureand the shell. The jacket or shell 74 is substantially stationary, beingconnected to the resonant bar structure 70 at a node of the latter. Thisexpedient effectively decouples the back side of the bar structure 76from the liquid outside. To assure that the diaphragm 8d will not besubject to an appreciable pressure differential, a conventional diversgas storage bottle 86, with a conventional aqua-lung pressure regulator87, feeds gas to the space inside the shell or jacket, at a pressureequal to that of the submergence pressure.

In FIG. 7 I have shown a sound wave radiation apparatus 100 inaccordance with the invention submerged by a cable 101 in a liquid body102 contained in a tank 103, which may, for example, be a tank section,in a tanker ship. This operates to radiate powerful sound waves in theliquid body. This apparatus is capable of removing solid foreignmaterial which has accumulated on and adhered to the inside surface ofthe tank. Moreover, the apparatus is especially effective for mixing thecontents, and preventing settling out of solids. The apparatus can bepermanently installed in an ocean liner or other tank, as well as beinginserted occasionally for short duration processing. In the case ofships tanks, the invention used as illustrated is especially effectivebecause of its high power. And because of its moderate frequency, sonicenergy loss through the hull is minimized.

FIG. 8 shows my sound wave radiator apparatus 110 in combination with anocean vessel 111, for locating the position and orientation of the soundradiator in the water. Here the apparatus is suspended by cables 112from conventional boom facilities on the vessel. The electric powersource may also be located on the ship, and power fed to the apparatusby cable 113. The dashed lines in the figure represent the soundradiation pattern if a simple form of my invention be used, givingradiation from the back as well as the front of the radiator 114. Thisis a dipole acoustic pattern, which places the vessel advantageously ina null region, and which is of advantage for establishing a standingwave pattern between a plurality of such ships.

FIG. 9 shows a monopole version of resonator-radiator in accordance withthe invention, given a radiation pattern primarily in one directiononly. It illustrates an anchored buoy 120 for supporting theresonator-radiator 121 of the invention through cables 120a. Here, thepower source may be on land, with an electric cable run out to the buoy,and thence, as at 122, down to the motor of the apparatus 121. Using asingle power source on land to feed a number of such units, theoperation thereof can be conveniently correlated as regards frequencyand/ or phase. As an alternative, the buoy may accommodate aconventional engine-generator 125 within it, supplying electric powerfor the electric motor of the apparatus. Here, additional governingmeans 126, of conventional type, can be radio controlled through antenna127 and conventional sensor 128 to govern the speed of the engine, andtherefore the frequency of the radiated wave.

It should be understood that a plurality of my resonator-radiator unitscan be closely spaced, so as to produce a beam, as taught in my PatentNo. 2,745,507.

In the foregoing specification and in the claims, I have used theexpression cyclic mechanical force generator. It is to be understoodthat such a device is of the broad class comprising an inertia masswhich moves through predetermined stroke limits with a component ofmovement relative to the case or body of the generator, and withconstraining means between the inertia mass and the core or body of thegenerator either as disclosed herein, or in the form of any of variousbearing arrangements, some variations of which are disclosed in my US.Patent No. 2,960,314.

The drawings and description will be understood to be merelyillustrative of and not restrictive on the invention considered in itsbroader aspects, and many modifi cations are therefore possible withinthe scope of the broader of the appended claims.

I claim:

1. A device for radiating sound waves into a body of liquid, comprising;an elongated member having a driving end and a radiating end, saiddriving end having a source of cyclic sound waves coupled thereto andsaid radiating end having means defining an enlarged liquid-contactingsurface, the sound waves produced by said source having a velocity nodespaced from said radiating surface a distance less than a quarter wavelength of said waves.

2. A device as defined in claim 1 wherein said member is of generallyhorn shape and comprises a single piece of elastic metal composition,the large end of said horn being said liquid-contacting surface.

3. A device as defined in claim 1 wherein said liquidcontacting surfaceis of a transverse dimension equal to a major fraction of a wave lengthin said liquid at the frequency of said source.

4. A device as defined in claim 1 wherein said source of cyclic soundwaves comprises a mass element movable cyclically and means reactivelycoupling said mass element to said driving end of said member.

5. A device as defined in claim 1 wherein said source comprises a bodyfixed to said driving end of said member and a mass element mounted onsaid body for oscillation relative to said body with a component ofmovement in the direction of length of said member whereby said bodyreceives a reactive oscillating force for transmission to said drivingend of said member.

6. A device as defined in claim 1 wherein said driving end is fartherfrom a velocity node in said member than is said radiating end.

7. A device as defined in claim 1 wherein the length of said member isgreater than a quarter wavelength of said waves and wherein saidvelocity node is between said driving end and said radiating end.

Horsley Mar. 4, 1952 Bodine Sept. 13, 1955

